Method of recovering glycerine from fermentation products



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United States Patent METHOD OF RECOVERING GLYCERINE FROM FERMENTATION PRODUCTS Justin Zender, Ardsley, N. Y., assignor to Glycerine Corporation of America, Inc., New York, N. Y., a corporation of Delaware Continuation of application Serial No. 204,494, January 4, 1951. This application March 30, 1954, Serial No. 419,933

9 Claims. (Cl. 210-8.5)

This application is a continuation of my copending application Serial No. 204,494 filed January 4, 1951.

This invention relates to recovery of glycerine from fermentation slops and is directed particularly to methods wherein the glycerine is extracted by dialysis through a semi-permeable membrane.

It has been suggested heretofore that glycerine might be recovered from fermentation slops by dialysis in a process wherein the slops and water are circulated on opposite sides of a semi-permeable membrane. In order to render such a process effective, the slops generally have to be concentrated to such an extent that they contain from about 20m 25% of glycerine. Even then, the aqueous dialysate generally contains only about 1 to 2% of glycerine and only about 40 to 70% of the glycerine can be extracted economically from fermentation slops by such a process even when using a continuous countercurrent process. Furthermore, the slops contain large amounts of inorganic salts which pass through the semipermeable membrane and are contained in the resulting dialysate. It is therefore necessary to carry out further purification steps in order to eliminate the inorganic salts from the glycerine so as to obtain a product capable of commercial use.

In accordance with the present invention, these objections to methods of the prior art are overcome and a process is provided wherein the glycerine content of the slops may be substantially less than heretofore necessary. Furthermore, the concentration of the glycerine in the dialysate is materially increased and the amount of glycerine extracted may be substantially quantitative. Of even greater importance is the fact that but very little of the inorganic salts are contained in the dialysate with the result that the glycerine obtained can be used directly in many commercial operations as, for example, as a 'plasticizing agent, or for use in the production of dynamite.

These advantages of the present invention are obtained by employing alcohols as the dialyzing liquid. While various alcohols and mixtures of alcohols may be used it is preferable to employ those which are miscible or soluble in water to some extent.

One of the objects of the present invention is to provide an economical method for the recovery of glycerine from fermentation slop.

Another object of the invention is to provide a method wherein glycerine is extracted from fermentation slops by dialysis using alcohols as the dialyzing liquid.

A further object of the invention is to provide methods whereby the glycerine extracted from fermentation slops by dialysis will be relatively free of inorganic salts and other impurities.

These and other objects and features of the present invention will appear from the following description thereof in which reference is made to typical procedures and examples for the purpose of indicating the nature of the present invention but without intending to limit the scope of the invention thereby.

In carrying out the present invention, the fermentation slops employed may be obtained from any suitable source. Thus, for example, the slops remaining after the distillation of alcohol from the products of fermentation of molasses with yeast, may be used. In the alternative, the products of fermentation of other sugar or starch containing products may be employed if desired. The method of fermentation may be varied and in a typical case is carried out by the fermentation of molasses under alkaline conditions, or in the presence of sodium sulfite and/or sodium bisulfite. The slops obtained by fermentation of molasses when using sodium bicarbonate or ammonia generally contain in the neighborhood at 2% of glycerine, whereas the concentration of the glycerine in slops obtained when sodium white and bisulfite are used may be as much as 6 or 8% or higher. In any event, it is preferable to concentrate the slops to some extent so as to increase the glycerine content before dialysis. The concentration may be carried out until the slops contain as much as 20 or 25%, as has been usual in conducting aqueous dialysis but, in accordance with the present invention, such concentration is not necessary and need not be more than 8 or 10%. In fact, the process is operable even when the slops are not concentrated at all and contain only 2 to 8% of glycerine although for economical and faster operation concentration of the slops is desired.

The fermentation slops resulting from the fermentation of molasses contain inorganic salts which generally include large amounts of calcium salts formed during the process of manufacturing the sugar and molasses. Additional salts are frequently introduced in adjusting the pH value of the fermentation mixture or as nutrient material for the yeasts employed. Such salts generally include calcium sulfate, calcium phosphate and various carbonates, sulfites and bi-sulfites. Sugar cane also is known to contain relatively large amounts of silicates, and therefore, various silicate salts may be present in the fermentation slops.

The dialyzing liquid employed in accordance with the present invention i preferably an alcohol or a mixture of alcohols. Normal and isopropyl alcohol and normal, secondary or tertiary butyl alcohol are preferred. Methyl and ethyl alcohol when used by themselves or in combination are found to cause diffusion of large amounts of inorganic salts and dark colored material or caramelized sugars to take place in dialyzing fermentation slops. Normal butyl alcohol can be used by itself and the dialysate obtained is bright and clear and contains substantially no inorganic salts. However, the diffusion of glycerine through the semi-permeable membrane when using normel butyl alcohol takes place relatively slowly. It thus appears that the rate of diffusion of both the glycerine and the inorganic salts through semi-permeable membranes is related in some way to the degree of solubility of the alcohol in water. It may, therefore, be said in general, that any alcohol which is soluble in water to the extent of 5% or more may be used in the practice of the present invention. Further, it has been found that excellent results are obtained when ethyl alcohol is mixed with the less soluble normal and secondary butyl alcohols. Mixtures containing equal parts of ethyl alcohol and normal butyl alcohol have been found to be very effective in carrying out the present invention. The alcohols which may be used in carrying out the present invention may further be defined as those which contain from 1 to 4 carbon atoms and preferably the alcohols containing 3 or 4 carbon atoms.

It is further desirable to maintain the alchol relatively concentrated and, in general, the dialysate should 'contain at least 50% and preferably or more of alcohol.

The semi-permeable membrane employed may be composed of any conventional hydrophilic material which is not dissolved or adversely effected by the alcohol. Typical of such membranes are regenerated cellulose, par-ehment paper, formalized gelatin, alkalisoluble-water 1nsoluble ethers, hydroxy cellulose and the like How ever, cellophane and particularly cellophane #300 has been found most useful in the dialyzing of fermentationfslops using isopropyl alcohol or mixtures of ethanol and butanol as the dialyzing liquid.

The process can be carried out at-room temperature but is preferably conductedat somewhat elevated temperatures, say around 28 to 32 C. Continuous countercurrent flow of the fermentationslops and alcohol fare desirable in orderthat the highest yield can beobtained in the minimum length of time. a t

A characteristicfeature of the present invention which distinguishes 'it materially from aqueous inrethod's of dialysis .resides in the fact that 'waten'pa'sses from the 'sl'ops "to the dialysa'te during the course of th'epresen't process and asa result, the slops tend to' become'jfur'ther concentrated and it is frequently necessary to add water or otherwise dilute the slops so as to keep them sufiiciently fluid for effective circulation through the dialyzing apparatus. This is incontrastjwith methods of "aqueous dialysis wherein the aqueous dialyzing medium penetrates themembrane and continuously dilutes the 's'lop's making it necessary 'to reconcentrate them from time to time. In accordance with the present invention it is the dialysate which is diluted by the water passing through the semipermeable membrane frorn the slops. Thusifstzitic-dialysis -is continu d for long periods of time the dialysate' needs 'to beconcentrated.

'In-order'to illustratetypical practice in accordance with the present invention, the following examples are cited.

Example 1 A fermentation liquor obtained after distillation of alcohol therefrom contained 10.05 grams per 100 cc. "of solids consisting of substances which remained after heating to 110 C. and including glycerine, salts, proteins, "gums and-other impurities. This liquor was concentrated and 100 ccs. of the concentrateplaced in a container formed of regenerated "cellulose and surrounded by anhydrous normal "butyl alcohol (which if soluble i'n'water only to the extent of about 8% After-24 hours o'f stat'ic dialysis the normal butyl aleoh'ol solvent wasfound to contain 211 grams of 'g'lycerine, ;066 gramof'salts and about grams 'of water whichha d diliu'sed through the membrane. representedjnearly 25% of the glycerine containedin the concentratewhe'reas less 'than- 1'%-of'thefsalts were extracted. The jdilfusate was {light amber in 'color and relativelyclearlas 'elojmpared with that obtained by dialysis using water "as the solvent,- indicating lmuch less difiusion'of the caramelized sugars and dark coloring agents of the slops.

By'repeating the static diffusion Wlth'fI'QSihjsOlVQDt or using continuous c'ounterfcurre'nt flow [of the solvent and fe'rm'entationliquor more than 90% of the .glycerine in'the concentrate can be recovered and it'is foundt'o contain only about 3% of salts as impurities. Therefore 'further treatment to obtain pure .glycerlin'e is simple and inexpensive. i

The .process ;of Example 'I- was repeated-.-using :a "concentrated fermentation slop containing 12.5 grams of glycerine and-56-grams of salts and other impurities gper 3100-668. The solvent-used was 91% isopropyl-alcohol. By using two -suc cessive static dialysis treatments 3.73 .grams of glycerine-and 1.99. grams of salts were recovered while 14 ccs. of water diffused through the membrane and served to-gdilute the isopropyl alcoholtsolvent. :The color of-vthe 'difiusate was ;a light amber. :The amount of -glycerinerecovered thus amounted toabout 3.0% of that contained in the concentrate, whereas only about th s t sqifiu q 1r 2 s -th -membr n 4 Example Ill When ethyl alcohol was used as the solvent with the concentrate of Example II the recovery of glycerine on two static treatments was 43%, but 18 ccs. of water diffused through the membrane and the amount of salts reeogered .was substantially higher than in the preceding examples. Moreover, 'thediffusion of caramelized sugars and other dark colored substances was substantial as indieatedby!the very-dark color of the dilfusate. The *glyce'rin'e thus obtained was not satisfactory for most practical purposes and would require substantial further puritieation hefot'e it could be usedin -general commercial tra s i Example ,"lV

Slops obtained-after thedistillationof alcohol from the products of fermentation of diluted molasses with dry afeast-pnder alkaline conditions, and initially-containing about 2% ofglycerine were concentrated until thejglyceripecontent was-8.26 The slops were continually pa on one -side of -a :form of cellophane #300 While 91%; isopropyl alcohol was continuously passeddncontact with the opposite side ofthe membrane. Dialyzing .wascentinued for. aperiod of 4% hours whereupon it was found that the dialysate contained 4.52% of glycerine and ';had.:extracted 85 of the glycerinefrom the fermentation S logs. The dialysate obtained contained only 0.34% ofsalts. The volume of alcohol employed was 131 times thevolume of the slops. The dialysate was distilled to remove the water and the resulting glyccrime .was of suflicient purity for use directly in the manufacture of dynamite.

0 Example V Fermentation "slops concentrated to contain 7.6% of g lycerine were "dialyzed in a continuous counter-current operation using 91 isopropyl alcohol in the "same r'n'annj'er as described'in Example I. The operation was con'tinuedfor a period of-'3 A hours whereupon it was found'tlia'tthe dialysate contained 3.32% of glycerine and represented a recovery of 992% of the glycerine contained in the slops. The amount of isopropyl alcohol employed was 126 times the amount of slops used in this Lexperiment. "Only'traces 'ofin'organicsalts were found in the-dialy'sate.

Example VI :Bermentation sl'op's ,and isopropyl alcohol were-passed in continuous counter-current relation with respect to a j'sernhpermeable membrane formed of cellophane #300. 250- parts of isopropyl alcohol were circulated per hour wghile pa1 '-ts of the slops were circulated ea'chhour. {The processwas continued for a .period of 20 hours. Theslgps contained 7.6% of glycerine and 7.06% 0f salts. The dialysate contained 3.13% of glycerineand 0.20%;ofsalts. The'totalamount of glycerine recovered was 172% of that-contained in the fermentation :slops.

:-Each of the foregoing examples was repeated using a mixtu're ofdll iparts ethanol and 50 parts normal butyl alcohol which was found to offer the advantages of each typer of alc'o'hol without their individual disadvantage. rhe antount "of 'gl'ycerine recovered was substantially the same in each case but the inorganic salts were'still limited -to"me're tra'ces in each instance so that the resultin'g g'lyce'rine was substantially pure.

In general, incarrying out the process of the present invention, the concentration of the glycerine in the ldialys'atejruns' from 3 to 6% and in excess of 70% of the "glycerine can be extracted from the fermentation slop s. In fact, substantially quantitative extraction can 'be etfected by. .prolonged dialysis although the slops tend togb'ecome so concentrated or dehydrated; that watergenerally -has to be added to maintain a -fluid condition.

While typical examples -=of .procedure -,in accordance with the present invention haverbeencited. ab'ove,-it -.will

be evident that the source of the fermentation material used as slops, the type of alcohol and the conditions of operation may be modified considerably without departing from the spirit and principle of the invention. In view thereof, it should be understood that the particular compositions, proportions and methods of procedure described above are intended to be illustrative only and are not intended to limit the scope of the invention.

What I claim is:

1. The method of recovering glycerine from fermentation slops which comprises the steps of placing the slops in contact with one side of a semi-permeable membrane and an alcohol which is soluble in water to the extent of at least 5%, on the opposite side of said semi-permeable membrane, and separating glycerine from the resulting alcoholic dialysate.

2. The method of recovering glycerine from fermentation slops which comprises the steps of passing the slops into contact with one side of a semi-permeable membrane and passing an alcohol which is soluble in water to the extent of at least 5%, in counter-current relation into contact with the opposite side of said semi-permeable membrane, and separating glycerine from the resulting alcoholic dialysate.

3. The method of recovering glycerine from fermentation slops which comprises the steps of concentrating the slops until the glycerine content thereof is about 8% or more, thereafter passing the slops into contact with one side of a semi-permeable membrane and passing an alcohol containing from 1 to 4 carbon atoms in countercurrent relation into contact with the opposite side of said semi-permeable membrane, and separating glycerine from the resulting alcoholic dialysate.

4. The method of recovering glycerine from fermentation slops which comprises the steps of passing the slops into contact with one side of a semi-permeable membrane and passing isopropyl alcohol in counter-current relation into contact with the opposite side of said semi-permeable membrane, and separating glycerine from the resulting alcoholic dialysate.

5. The method of recovering glycerine from fermentation slops which comprises the steps of passing the slops into contact with a mixture containing equal parts of ethyl alcohol and secondary butyl alcohol in countercurrent relation into contact with the opposite side of said semi-permeable membrane, and separating glycerine from the resulting alcoholic dialysate.

6. The method of recovering glycerine from fermentation slops which comprises the steps of placing the slops in contact with one side of a semi-permeable membrane and placing a mixture of alcohols containing from 1 to 4 carbon atoms, at least half of which alcohols contain at least 3 carbon atoms, on the opposite side of said semipermeable membrane while maintaining the temperature of the slops and dialysate at about 28 to 32 C.

7. The method of recovering glycerine from fermentation liquids which comprises the steps of passing said liquid in contact with one face of a hydrophilic semipermeable membrane, passing a liquid containing at least of a mixture of alcohols which contains from 1 to 4 carbon atoms, at least half of which alcohols contain at least 3 carbon atoms, in contact with the opposite face of the membrane, and separating glycerine from the resulting alcoholic dialysate.

8. The method of recovering relatively salt-free glycerine from fermentation slops containing a high percentage of inorganic salts which comprises the step of passing said slops into contact with one face of a hydrophilic semi-permeable membrane while passing a mixture of alcohols containing from 1 to 4 carbon atoms, at least half of which alcohols contain at least 3 carbon atoms, ,in contact with the opposite face of the membrane, and separating the alcohol from the relatively salt-free glycerine containing difiusate thereby obtained.

9. A process for recovering relatively salt-free glycerine from fermentation slops containing large amounts of inorganic salts which comprises the steps of passing the fermentation slops across one face of a hydrophilic semi-permeable membrane, passing across the other face of said membrane an aqueous liquid containing at least 50% of a mixture of alcohols each of which contains from 1 to 4 carbon atoms, and at least half of which contain at least 3 carbon atoms, directing the flow of the slops and alcohol counter-current to each other, evaporating off the alcohol from the resulting alcohol-glycerine solution, and recirculating the alcohol across said membrane.

References Cited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS Great Britain Aug. 21, 1931 

1. THE METHOD OF RECOVERING GLYCERINE FROM FERMENTATION SLOPS WHICH COMPRISES THE STEPS OF PLACING THE SLOPS IN CONTACT WITH ONE SIDE OF A SEMI-PERMEABLE MEMBRANE AND AN ALCOHOL WHICH IS SOLUBLE IN WATER TO THE EXTENT OF AT LEAST 5%, ON THE OPPOSITE SIDE OF SAID SEMI-PERMEABLE MEMBRANE, AND SEPARATING GLYCERINE FROM THE RESULTING ALCOHOLIC DIALYSATE. 